Electrical insulator



Sept. 14, 1937. A MAUNOVSZKY 2,092,982

ELECTRICAL INSULATOR Filed June '8, 1936 0 A/vofw mL//voVJz/ry 1N VEN TOR.

ATTORNEY.

Patented Sept. 14, 1937 UNITED STATES PATENT OFFICE 2 Claims.

This invention relates to electrical insulators, and in particular to concealed strain insulators for high tension electric transmission lines. They Object of the invention is to provide an insulator having high mechanical strength combined with high electrical insulating properties. Another object is to provide a strain insulator in which the metallic parts are almost wholly enveloped by the dielectric material, and protected from, temperature changes and climatic and corrosive influences. Still another object is to provide a strain insulator in which advantageous dielectric properties and ohmic resistances are maintained during use.

I'hese and other objects are attained by the arrangement and combination of parts shown in the accompanying drawing in which Fig. 1 is a vertical sectional view of one form, of my invention.

Fig. 2 is a plan view of the insulator shown in Fig. 1.

Fig. 3 is a vertical sectional view of another form of my invention.

Fig. 4 is a transverse sectional View taken on the line 4-4 of Fig. 3.

Fig. 5 is an elevation, partly in section, showing another form of my invention.

Fig. 6 is an isometric View of the main ceramic body of Fig. 1.

It is important in high tension insulators that not only should the high insulating value be maintained under all weather conditions, but also that the insulator should have high mechanical strength to resist the strains to which it is subjected in use. It is also important that even under adverse conditions the line should not be allowed to fall to the ground, with consequent danger to life, and the interruption of service. The insulating and dielectric parts of outdoor insulators are commonly made of vitried ceramic materials, and it is this type of material which I utilize in my insulator, although I prefer a particular composition discussed below. It is well known that vitrii'led ceramic materials are much stronger under compressive load than under tension, and I take advantage of this fact in my device. It is also well known that thermal strains, for example from the sun shining on only one side of an insulator, cause mechanical shocks which produce cracks and checks, and ultimately permit moisture to penetrate the body and reduce its insulating value. It is also well known that high temperatures lower the dielectric strength of ceramic insulating material, and that altermating currents cause stresses in a dielectric mawithin the following composition range. 10

Parts per Dumortierite 30 to 70 Ball clay 10 to 20 Kaolin 2O to 30 g Tremolite 10 to 30 la These materials are ground ne so that they will pass approximately a mesh screen, are then mixed into a slip with water, and the excess Water removed by lter-pressing. The articles 20 are then cast, moulded, or formed by the usual methods, and after suitable drying, the shapes are burned to temperatures corresponding to cones I4 to I8. At these temperatures of iring, a natural glaze forms on the surfaces, which 25 makes the pieces impervious to moisture.

Referring to the drawing, Figs. 1 and 2 represent a simple form of my insulator. The main body II is cylindrical in shape with the ends recessed for seating the caps I3 and I4, and hav- 30 ing two pairs of holes, I5 and I6, and I'I and I8, provided lengthwise of the cylinder body II for receiving the legs of U bolts 25 and 26, the curved portion of one U bolt 25 being seated in the recess under the cap at one end of the main body 35 II, and the curved portion of the other U bolt 26 being seated in the opposite recess. The planes of the two U bolts 25 and 26 are disposed at right angles to each other, with the U opening facing in opposite directions, and in space nterlinked with the porcelain body between them. The end caps I3 and I4 are apertured to allow the legs of the U bolts to protrude, and are so shaped that they substantially ll the recesses at the ends of the ceramic main body II, and 45 having a protruding portion 21 adapted to fit around the curved portions of the U bolts in the grooves into which said U bolts are seated. The spaces around the U bolts and between the caps I3 and I4 and the main body portion II, 50 are iilled with a suitable cementing material, so that when assembled the insulator is sealed and the internal metal portions protected from weathering and corrosion. Eyelets or hooks or other attaching means are connected to the pro- 55 truding ends of the U bolts, a connecting plate 28 with attached eyelet 29 between the two legs being shown in the drawing. The ends of the U bolts are threaded for nuts 3l] and expansion washers 3l are preferred to take up the diierences in thermal expansion of the metal and ceramic parts.

The modification of my invention shown in Figs. 3 and 4 has the main ceramic body I I, with caps I3 and I4, and U bolts 25 and 26, similar to those in Figs. 1 and 2. There is provided, in addition, an outer ceramic cylinder 32 having an air space G2 between it and the main cylindrical body II, which outer cylinder is held in position by groove 33 in the outer cap 34 and the collar 3S in the lower outside cap 35, fitting over the inner caps I3 and I4. I'hese outer caps 34 and 35 are extended to provide umbrella skirts or petticoats 36 and 3l for shedding rain and snow, and these skirts are preferably provided with concentric ribs or rings 38 which lengthen the path for surface electrical discharges, or flash-over from one metallic part to another. The air insulating space between the outer and the inner cylinders prevents unequal heating of the inner parts, and the outside cylinder and caps also provide protection to the inner cylinder from dust and moisture accumulation. rIhe parts are all held together by the nuts and expansion washers on the U bolt legs. The inner and outer caps may also be made in single pieces.

Another form of my invention is shown in Fig. 5, which is similar in construction to Fig. l, but having a petticoat 36 intermediate the end caps for shedding rain and snow. This petticoat is preferably made integral with the main cylinder II, but may be made separate and attached by well known means.

While I have illustrated and described several modications of my invention, I do not limit myself to the particular forms shown, but restrict my invention only insofar as necessitated by the prior art and by the spirit of the appended claims.

I claim:

l. An electrical strain insulator comprising a cylindrical body of ceramic composition adapted to envelope and support in spaced relation two interlinked U bolts and having a portion of its ceramic mass interposed therebetween, said two metallic U bolts having substantially parallel legs interlinked in spaced relation within said cylindrical body, and two end caps of ceramic composition having apertures respectively for each pair of legs of said U bolts, said end caps having integral protruding plugs adapted to seal up the interlocked portions of the U bolts, means including expansion gaskets associated with said U bolts for attaching the caps to the cylindrical body, and attaching means associated with opposing pairs of protruding legs of said U bolts.

2. An electrical strain insulator comprising a cylindrical body of ceramic composition adapted to envelope and support in spaced relation two interlinked U bolts and having a portion of its ceramic mass interposed therebetween, said two metallic U bolts having substantially parallel legs interlinked in spaced relation within said cylindrical body, two end caps of ceramic cornposition having apertures for the legs of said U bolts, an outer cylinder of ceramic composition spaced away from said cylindrical body, an upper skirted cap of ceramic composition apertured for the` legs of one of said U bolts, a lower skirted cap of ceramic composition apertured for the legs of the other of said U bolts, said upper and lower skirted caps being adapted to space said outer cylinder from said inner cylindrical body, means including expansion gaskets associated with the protruding legs of said U bolts for holding the assembly together, and means associated with the respective pairs of legs of the opposing U bolts for supporting said insulator in strain.

ANDREW MALINOVSZKY. 

